A variety of observations are employed to conduct a preliminary analysis of the propagation in solar-interplanetary space of seven earth-directed full-halo coronal mass ejections (CMEs) originated from the solar active region (AR) 3664 from May 8 to 11, 2024. These seven CMEs can be divided into two groups. The first group consists of four CMEs that occurred during the period from 05: 36 UT on May 8 to 9: 24 UT on May 9, and the second group consists of three CMEs that occurred during the period from 18: 52 UT on May 9 to 1: 36 UT on May 11. We utilize the heliospheric imager on the Solar Terrestrial Relations Observatory A (STEREO A/HI) to observe and track the time-elongation relationships of the high-density regions corresponding to these two groups of CMEs, and apply the fixed-Φ angle fitting method and the harmonic mean fitting method to calculate the most probable propagation directions and average radial velocities of these two groups of CMEs. The results show that the high-density regions associated with these two groups of CMEs are respectively aliased in the field of view of STEREO A/HI. The minimum errors of two group CMEs' arrival times near the Earth's orbit calculated from the fitting radial velocities are 0.5 hours and 3 hours respectively. These results indicate that during the solar-terrestrial propagation of these two groups of CMEs, the fast CMEs behind catch up with the slower CMEs ahead, thus, the two groups of CMEs form two complex ejecta and generate the extremely intense geomagnetic storm.
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